Balanced slicing silencer



Oct. 27, 1.942. v H. MocuRDY 2,300,130

BALNCED SLCING' SILENCEB Filed Nov. 19, 1940 Patented Oct. 27, 1942 UNITED STATES PATENT OFFICE BALANCED sLloING SILENCER Howard McCurdy, Walnut Park, Calif. Application November 19, 1940, serial No. 366,207

6 Claims.

This invention is a muflier or silencer for the reduction of discharge velocity and incidental noise of fluids expanding` under pressure; more particularly gaseous fluids.

It is an object of this invention to provide means, in a muffler or silencer shell, in the form of a helical ribbon to form, along the inner face of the shell, a helical expansion chamber, and the ribbon being of a gradually changing width, that is in dimension transverse to the axis of the shell, and therefore forming an expansion chamber which equallychanges in radial depth from the axis. Further, the said ribbon is constructed, proportioned and arranged so that it provides a slicing-effect lip to a fluid stream passing in the shell and the said lip is so helically turned and spaced from the shell axis that the lip edge forms a central, unobstructed flow passageway or bore for the length of the silencer.

In such a structure as just described there may be a tendency for the stream to set up a rotation of its mass that remains unsliced in and along the said bore and an object is to provide means in nowise obstructing axial or transverse flow of the stream outwardly as to the axis and for the purpose of thwarting the rotational tendency in the bore stream and without retarding a helical flow of the sliced portions of the fluid in the expansion chamber.

Since a fluid stream will seek the line of flow of least resistance if only one helical, bore forming ribbon is fixed in the shell and along its wall surface the stream will tend to crowd or sinuously bend from side to side of the axis to avoid the edge of the ribbon (especially when this is of wide pitch) and defeat the desired lateral expansion of the fluid and the present invention includes the provision of a multiplicity of the slicing ribbons in such balanced relation that if the stream tends to bend away from one lip it must move toward one in an opposite relation; the two opposing lips thus having a balancing effect of each taking a slice at opposite sides of the bore stream.

The invention consists in certain advancements in this art as set forth in the ensuing disclosure and having, with the above additional objects and advantages as hereinafter developed, and whose constructions, combinations and details of means, and the manner of operation will be made manifest in the following description of the herewith illustrative apparatus; it being understood that modifications, variations and adaptations may be resorted to within the spirit,

scope and principle of the invention as it is more particularly claimed presently.

Figure l is a partly sectioned, side elevation of the preferred form of thevsilencer. Figure 2 is an elevation of a convergent outlet cap or end for use in some applications of the silencer. Figure 3 is a cross-section showing a triple-ribbon form. Figure 4 is a section showing differential slant of the ribbon at successive cross-planes along the shell.

The shell 2 is preferably of truncated-cone form and of right-line side wall characteristic and has an inlet tube 3 joined to a flared throat 4 at the large end of the shell. The shell may be unobstructedly open at its smaller end for some usesfas in Fig. l, but there is shown in Fig. 2 a converged dome or cap 5 with a central, that is, axial, outlet muzzle 6.

Suitably fixed to and along the inner face of the shell is a helical-form means in the form of preferably more than one helical ribbon or flange like element; Fig. 1 showing two equipitch ribbons I 0-l0 so that portions of their coils occur at diametrically opposite points all along the shell. One feature of this invention is that each ribbon is of gradually changing width from its inner, lip forming edge I0 outward to the enclosing shell 2, and this change of width is such that the lip I0 is at a uniform distance for its length from the shell axis.

Another feature of the invention is that the ribbon I0 has its cross-section plane at any point slanted inwardly and, in the illustrated forms, toward the intake end 4 and therefore are highly effective in taking off annular portions of the fluid stream meeting the intruded ribbon edge or lip l0. Since the intake end of the silencer is its larger end it will be seen that the incoming fluid having the highest degree of pressure is first sliced by the first intercepting lip 2a and is diverted radially to an expansion cell 2b of the largest capacity of the series which is formed along the shell 2 between the successive coils of the ribbons and which cells as between successive lips 2a gradually diminish in volume toward the outlet of the silencer. It will be seen that the helical lip l0 forms a straight bore of uniform diameter for the length of the ribbon or ribbons, axially. The helical space formed between the ribbons for their full helical length constitutes a substantially unobstructed flow passageway for the expanding slices of fluid which are cut by the lips from the core or stream of fluid traversing the bore along the ribbon lips; this bore being unobstructed.

By the provision of plural ribbons l0 and I0 in the shell the bore stream is kept in a straight path and prevented from leaning away from an intercepting, slicing lip 2a at any point in the passageway or bore; in other words a balanced cutting eiect is maintained.

The expanding fluids that have been diverted out into the helical passageways may at once set up a helical sweep along the passageway but it is desired to prevent fluid immediately at the rearward face of the ribbons and especially just back of the lips from taking on a rotary swirl. Therefore there are fixed on the said rear faces of the ribbons a number of radial blade-like arresters or check plates l5 of suitable height. and length from the lips l0. In Fig. 1 these checks are arranged at about 90 degrees annularly along the ribbons. By this arrangement undesired stream rotation is arrested and at the same time the bore of the ribbons device is both laterally and longitudinally unobstructed, as would be desired when the silencer is adapted for use on fire-arms.

Fig. 4 illustrates a form in which the slicing blade or ribbon I0 is of gradual changing obliquity for its length as to the shell axis as well as of gradually changing width; the greatest slant being at the intake end. Triple function is here secured, highest slicing efliciency at the inlet where the iluid pressure is highest-largest expansion breast for the first slice, and greatest width of hood surface for silencing of noise.

In this form of silencer a feature of the device is that it provides for greater expansion of the wave front from the bore to the shell circumference and then greater helical periphery travel while the fluid expands. In other words CII the fluid must exhaust its energy while in its greatest expansion breast, and is held at that breast until it does lose energy.

What is claimed is:

1. A fluid expanding silencer including a frusto-conic shell having an axial passageway and helical slicing lips along the passageway and in diametrically opposite relation whereby the lips coact in a balance action on the flowing stream.

2. A fluid expanding silencer including a frusto-conic shell having helical slicing ribbons xed along its inner face and whose inner edges form a uniform bore or stream passageway axially of the shell; the ribbons being in equiangular relation for flow balancing effect.

3, In a silencer of the class set forth; a shell, and' a fluid slicing ribbon helically arranged about the shell axis and being of gradually decreasing radial width along the axis.

4. The silencer of claim 3; and the ribbon being of gradually changing obliquity, in crosssection, as to the shell axis.

5. The silencer of claim 2; and rotation checking means fixed to the ribbons in a position ex ternal to the said bore.

6. A silencer shell having internal means including symmetrically, annularly spaced ribbons in cell--iorming axially spaced relation and having inner slicing edges concentric to the shell axis to form a ow bore, and rotation checking means fixed to the ribbons and clear of the said bore; the ribbons coacting to keep the stream in a generally direct bore path.

HOWARD MCCURDY. 

